**Word Problem**: A projectile is fired from the top of an 80 foot building with an initial velocity of 64 feet per second. The height of the projectile in feet after

*t*seconds is given by the following function and its graph.

a. Use the graph to determine how long it takes to reach the maximum height.

b. How much time will it take to hit the ground?

c. What is the height of the projectile after 4 seconds?